"On June 21, The China Coast Guard (CCG) 2502 fleet patrolled the territorial waters of our Diaoyu Islands. This is a rights protection patrol in accordance with the law," the statement said.
In May, Japanese media reported that two Chinese government vessels traveled close to the disputed islands. In June, the Japanese government sent two separate protest notes to China after the entry of a Chinese research vessel into the territorial waters around the islands. The second protest note was sent after Chinese patrol vessels followed.
Both Japan and China have extended territorial claims over the islands. Japan insists on its sovereignty over the Senkaku islands effective since 1895, while China points to Japanese maps from 1783 and 1785 designating the islands as Chinese territory. After World War II, the islands went under the control of the United States and were passed on to Japan in 1972.
Japan believes that China's sovereignty claims over the islands were prompted by the discovery of valuable minerals in their shelf waters in the 1970s. The territorial dispute escalated in 2012, when the Japanese government purchased three of the five islands from a private owner, thereby confirming Japan's affiliation with the islands.